Biomedical subjects

Yasuhiro Kakazu

Publications and source records attributed to Yasuhiro Kakazu.

10 recordsLinked to original sources

PubMed2006

Bilirubin potentiates inhibitory synaptic transmission in lateral superior olive neurons of the rat.

Bilirubin is a well-known neurotoxin that can result in multiple neurologic deficits. Previous studies have suggested that bilirubin affects aspects of synaptic transmission; however the acute effects of bilirubin on synaptic transmission have not been examined in real-time. In this study, using whole-cell voltage-clamp recordings, we observed the effect of bilirubin on inhibitory postsynaptic currents (IPSC) in postnatal 13-15-day-old neurons dissociated from lateral superior olive nuclei (LSO), one of the brainstem auditory nucleus that are highly vulnerable to bilirubin. The results showed that 10(-5)M bilirubin increased the frequency of spontaneous IPSC without causing change in their amplitudes or in the response to bath applied glycine, suggesting a presynaptic locus for the action. In the presence of tetrodotoxin, the frequency of miniature IPSC was also potentiated by 10(-5)M bilirubin. The facilitation by bilirubin was concentration dependent and increased with an increase in exposure time. Bicuculline only partially reduced the action of bilirubin. The action of bilirubin was observed in extracellular Ca(2+)-free ([Ca(2+)](o) free) solution but was fully occluded by pretreatment with BAPTA-AM in [Ca(2+)](o) free solution. Thus, in LSO neurons, bilirubin facilitates inhibitory synaptic transmission, in a manner independent of voltage-activated Na(+) and Ca(2+) channels but dependent on presynaptic [Ca(2+)](i). The increase of inhibitory synaptic transmission in response to acute bilirubin is a novel effect of bilirubin on the central nervous system and may have implications for neurotoxicity and the impairment of auditory transduction seen in hyperbilirubinemia.

Animals↗

PubMed2006

Intractable otitis media with eosinophils: Importance of diagnosis and validity of treatment for hearing preservation.

This study investigated hearing levels in cases of intractable otitis media with eosinophils and validated the treatment strategy. Medical charts were reviewed retrospectively. The diagnosis was made when the proportion of eosinophils in middle ear secretions exceeded 10%. Twelve patients were identified and treated with an antihistaminergic agent, leukotriene receptor antagonist and topical steroid. The air-bone conductance gap decreased significantly with the relief of subjective symptoms. Bone conduction hearing levels at 4 and 8 kHz were higher than at lower frequencies. There was a significant correlation between subjective symptom duration and bone conduction hearing level at 8 kHz, which diminished with treatment. Compared with suppurative otitis, active otitis with eosinophilia damages high-tone sensory hearing in a time-dependent manner, and antiallergic treatment prevents progression of the high-tone sensory hearing loss. We emphasize the importance of diagnosis and the validity of treatment for intractable otitis media with eosinophils.

Adult↗

PubMed2006

Squamous cell carcinoma of the external auditory canal and middle ear: an operation combined with preoperative chemoradiotherapy and a free surgical margin.

OBJECTIVE: Treatment outcomes for squamous cell carcinoma of the temporal bone were evaluated regarding stage, therapeutic strategy, and prognostic factors. STUDY DESIGN: Retrospective case review. SETTING: University hospital and outpatient clinic. PATIENTS: Twenty-five patients with primary squamous cell carcinoma of the external auditory canal and middle ear. INTERVENTION: Preoperative chemoradiotherapy and radiotherapy were used in 7 of 12 patients. Lateral temporal bone resection was performed for the lesions not beyond the tympanic membrane. Subtotal temporal bone resection was chosen for lesions extending to the middle ear cavity when there was no invasion to the pyramidal apex, carotid canal, or dura or metastasis. Others were conservatively treated by chemoradiotherapy. When the performance status was poor or an agreement regarding the operation could not be reached, the treatment was modified. MAIN OUTCOME MEASURE: Estimated survival rates. RESULTS: The 3-year estimated survival for T1 and T2 lesions was 100%. The 5-year estimated survival for T3 and T4 lesions was 80% and 35%, respectively. The 5-year estimated survival improved up to 75% for T4 tumors with operation and 16% for those without operation after 47 months. The tumor-free surgical margin is significantly related to patient survival in T3 and T4 lesions. Multivariate analysis predicted that concomitant chronic otitis media and positive lymph nodes were significantly associated with poorer survival. CONCLUSION: The tumor-free surgical margin was important to survival. When T4 lesions did not involve the pyramidal apex, carotid canal, dura, or any lymph nodes, the surgical intervention improved the estimated survival rate to a level as good as T3 lesions.

Adult↗

PubMed2005

GABA-induced response in spiral ganglion cells acutely isolated from guinea pig cochlea.

The physiological and pharmacological properties of gamma-aminobutyric acid (GABA)-induced responses were investigated in acutely isolated spiral ganglion cells (SGCs) of guinea pig by using either a nystatin-perforated patch recording configuration or a conventional whole-cell patch recording mode combined with rapid drug application. GABA and GABA(A) subtype receptor agonist, muscimol, induced inward currents in a concentration-dependent manner in 74% of all cells. The current-voltage relationship for the GABA response indicated the GABA-induced current in SGCs is carried by Cl-. Bicuculline (BIC), strychnine (STR), and picrotoxin (PTX) suppressed the GABA response in a concentration-dependent manner. BIC and STR, and PTX blocked the GABA response in a competitive manner and in a non-competitive manner, respectively. For inorganic antagonists, Cd2+ and Ni2+ also inhibited the GABA response. On the other hand, Zn2+ failed to suppress the GABA response in SGCs. An antibiotic, benzylpenicillin, suppressed the GABA response. The GABA response was augmented by both a barbiturate derivative, pentobarbital (PB), and a benzodiazepine derivative, diazepam. The results suggest clearly that the physiological and pharmacological characteristics of GABA(A) receptor on acutely isolated guinea pig SGCs are quite similar to the common GABA(A) receptor found in other sensory ganglion cells.

Animals↗

PubMed2005

Effective comparison of two auto-CPAP devices for treatment of obstructive sleep apnea based on polysomnographic evaluation.

BACKGROUND: Automatic continuous positive airway pressure (auto-CPAP) machines differ mainly in algorithms used for respiratory event detection and pressure control. The auto-CPAP machines operated by novel algorithms are expected to have better performance than the earlier ones in the treatment of obstructive sleep apnea syndrome (OSAS). OBJECTIVES: The purpose of this study was to determine the therapeutic characteristics between two different auto-CPAP devices, i.e., the third-generation flow-based (f-APAP) and the second-generation vibration-based (v-APAP) machines, during the first night treatment of OSAS. METHODS: We retrospectively reviewed the polysomnography (PSG) recordings of 43 OSAS patients who were initially performed an overnight diagnostic PSG to confirm the disease and afterwards received the first night auto-CPAP treatment with using either the f-APAP (n=22) or v-APAP (n=21) device under another PSG evaluation. RESULTS: There were 13.6% and 61.9% patients who remained a residual apnea/hypopnea index more than 5 during the f-APAP and v-APAP application, respectively (P<0.005). The f-APAP was more effective than the v-APAP in reducing apnea/hypopnea index (P=0.003), hypopnea index (P=0.023) and apnea index (P=0.007), improving the lowest oxygen saturation index (P=0.007) and shortening stage 1 sleep (P=0.016). However, the f-APAP was less sufficient than the v-APAP in reducing arousal/awakening index (P=0.02). CONCLUSION: These findings suggest that the f-APAP works better than the v-APAP in abolishing breathing abnormities in the treatment of OSAS; however, the f-APAP device might still have some potential limitations in the clinical application.

Adult↗

PubMed2004

Experience-dependent changes in intracellular Cl- regulation in developing auditory neurons.

A developmental change in GABA and glycine responses, from a depolarization to a hyperpolarization, have been reported for a range of CNS neurons, and has been demonstrated to be due to a developmental decrease in the intracellular Cl- concentration ([Cl-](i)). We examined [Cl-](i) in isolated rat lateral superior olive (LSO) neurons using patch-clamp recordings of glycine gated Cl- currents and by measuring intracellular Cl- -fluorescence. In neurons from 14-16-day-old rats (P14-P16), which had previously received unilateral or bilateral cochlear ablations before the onset of hearing, there was no developmental decrease in [Cl-](i). No significant differences in [Cl-](i) were observed amongst rats with either ipsi- and contralateral ablations. Implanted strychnine pellets also prevented the decrease in [Cl-](i) in most neurons. In some of these neurons in which [Cl-](i) remained high, there was a lack of expression of the K+-Cl- cotransporter 2 (KCC2) mRNA. These results demonstrate that the developmental decrease in [Cl-](i) in LSO neurons is dependent on neuronal activity and that both GABAergic/glycinergic and glutamatergic afferent activity contribute to this maturation of the Cl- regulatory mechanisms.

Acoustic Stimulation↗

PubMed2003

Developmental switch from GABA to glycine release in single central synaptic terminals.

Early in postnatal development, inhibitory inputs to rat lateral superior olive (LSO) neurons change from releasing predominantly GABA to releasing predominantly glycine into the synapse. Here we show that spontaneous miniature inhibitory postsynaptic currents (mIPSCs) also change from GABAergic to glycinergic over the first two postnatal weeks. Many 'mixed' mIPSCs, resulting from co-release of glycine and GABA from the same vesicles, are seen during this transition. Immunohistochemistry showed that a large number of terminals contained both GABA and glycine at postnatal day 8 (P8). By P14, both the content of GABA in these mixed terminals and the contribution of GABA to the mixed mIPSCs had decreased. The content of glycine in terminals increased over the same period. Our results indicate that switching from GABAergic to glycinergic inputs to the LSO may occur at the level of a single presynaptic terminal. This demonstrates a new form of developmental plasticity at the level of a single central synapse.

Animals↗

PubMed2002

Allopregnanolone enhancement of GABAergic transmission in rat medial preoptic area neurons.

Gamma-aminobutyric acid (GABA)-mediated transmission in the medial preoptic area (MPOA) of the hypothalamus plays an important role in functions such as sex steroid hormone dynamics and control of body temperature. The action of allopregnanolone, the primary metabolite of progesterone, on GABAergic transmission was investigated by employing patch clamp whole cell recording on acutely dissociated rat MPOA neurons with the functional connection of presynaptic terminals. Allopregnanolone enhanced spontaneous GABA release on the MPOA neurons and induced prolonged decay of miniature GABAergic-inhibitory postsynaptic currents (mIPSCs). The facilitation of GABA release from the presynaptic terminals by allopregnanolone disappeared in Ca2+-free extracellular solution. The presynaptic action of this neurosteroid was also blocked by bumetanide, a blocker of cation-Cl- cotransporters, and by removal of extracellular Na+. The results suggest that allopregnanolone enhances GABAergic transmission at the MPOA neurons by pre- and postsynaptic mechanisms. The enhancement of GABA release by allopregnanolone might require a high Cl- concentration in the presynaptic terminal maintained by Na+-dependent, bumetanide-sensitive mechanisms (e.g., Na+-K+-Cl- cotransporter) and might be mediated by Ca2+ influx into presynaptic terminal.

Animals↗

PubMed2002

Na(+)/Ca(2+) exchanger in GABAergic presynaptic boutons of rat central neurons.

Rat Meynert neurons were acutely isolated using a dissociation technique that maintains functional GABAergic presynaptic boutons. Miniature inhibitory postsynaptic currents (mIPSCs) were recorded under voltage-clamp conditions using whole cell patch-clamp recordings. Using the frequency of mIPSCs as a measure of presynaptic terminal excitability, the existence of a Na(+)/Ca(2+) exchanger (NCX) in these GABAergic nerve terminals was clearly demonstrated. Both the frequency and the amplitude of mIPSCs were unaffected by replacement of extracellular Na(2+). However, in this Na(+)-free external solution, ouabain could now induce a transient increase of mIPSCs frequency, which was not inhibited by adding Cd(2+) or cyclopiazonic acid but was inhibited by removing external Ca(2+). This indicates that this transient potentiation was dependent on external Ca(2+), but that this Ca(2+) influx was not via voltage-dependent Ca(2+) channels. KB-R7943, an inhibitor of NCX, at a concentration of 3 x 10(-6) M, reduced this transient increase of mIPSCs frequency without affecting mIPSCs amplitude and the response to exogenous GABA. These results demonstrate the existence of NCX in these GABAergic nerve terminals. In zero external Na(+), ouabain causes an accumulation of intraterminal Na(+) and a resultant influx of Ca(2+) through the reversed mode operation of NCX. However, under more physiological conditions, NCX may also operate in a forward mode and serve to maintain low intracellular [Ca(2+)] in nerve terminals.

Animals↗

PubMedDate not supplied

Multidimensional voice evaluation in pretreatment glottic carcinoma.

It is generally accepted that, in glottic carcinoma, the voice will deteriorate, even in the early stages. This paper reports the degree of hoarseness and multidimensional vocal evaluation of glottic carcinoma patients. Forty-seven male glottic carcinoma patients and a control group of 13 normal subjects were included in this study involving psychoacoustic evaluation by doctors, acoustic analysis, phonogram, maximum phonation time and stroboscopy before treatment. A normal voice or mild hoarseness by psychoacoustic evaluation was found in 35% of cases with T1 and T2 glottic carcinoma. Patients with psychoacoustically inferior vocalization had high scores on acoustic analysis, small phonogram areas, and short maximum phonation time. Stroboscopy revealed attenuation or disappearance of the mucosal wave on the tumor side in all cases, whether the acoustic analysis data were within or beyond the normal limits. We identified two conditions offering superior vocalization in glottic carcinoma patients: (1) the lesion should be unilateral, and (2) the lesion should be flat with no protrusion. We should evaluate patients with glottic carcinoma not only with vocal examination but also using stroboscopy before biopsy.

Adult↗